As the center of human activities and social civilization, city has developed at the cost of serious environmental degradation and huge eco-environmental pressure, which further lower the human living standard and impeded the sustainable development of the urban ecosystem. Current urban metabolic methods have broader views and focus more on ecological aspects——impact of emissions and resource consumption ― but they lack a rigorous thermodynamic framework. Consequently, there is a need for modifying existing processes and developing new technologies that minimize environmental impact while providing stimulating ecological flow. This study developed an emergy-based framework for evaluating ecological objectives in traditional urban metabolic process. It started with a brief historical review of urban sustainable development and examines the controversial concept critically from a thermodynamic point of view. Then the assessment framework was proposed by reviewing and compiling existing data and studies on environmental issues available primarily at some sources, which includes resource accounting and environmental impact assessment. The direct and indirect emergy demand was assessed and quantied based on airborne/waterborne pollutants dilution patterns, and concepts of Life Cycle Impact Assessment. Such a framework is a necessary pre-requisite to perform a reliable cost-benefit evaluation of urban sustainability strategies, and provide guidance to policy decisions.